Preparation of phosphonothioic dichlorides, tetrachlorophosphoranes, and phosphonic dichlorides



PREPARATION OF PHOSPHONOTHIOIC DICHLO- RIDES, TETRACHLORGPHOSPHORANES, AND PHOSPHONIC DHCHLORIDES Hans Z. Lecher, Plainfield, and Ruth A. Greenwood,

Somerville, N. J., assignors to American Cyanamitl Company, New York, N. Y., a corporation of Ma ne No Drawing. Application March 25; 1955 Serial No. 496,948

19 Claims. (Cl. 260-543) This invention relates to a new process for making phosphonothioic dichlorides, RPSCI and tetrachloro: phosphoranes, RPCl which can be readily transformed into phosphonic dichlorides, RPOCl by knownmethods.

Phosphonothioic dichlorides and phosphonic dichlor des are starting materials for esters, amides and ester-amides of phosphonothionic acids and of phosphonlc acids which are of interest in the fields of pesticides, lubricating 011 additives and flame-resistant resins.

The intermediate dichlorides in which R is an aryl group have been prepared in the past by various methods which were both cumbersome and expensive. A more direct method of preparing aryl-phosphonic dichlorides 18 described and claimed in the copending applications of Lecher, Chao and Whitehouse, Serial No. 345,264, filed March 27, 1953, now U. S. Patent 2,717,906, issued September 13, 1955, and Greenwood, Scalera, and Lecher, Serial No. 357,368, filed May 25, 1953 now Patent No. 2,814,645. In these processes aromatic compounds free from polar groups capable of reacting with phosphor c anhydride were phosphonated withhexagonal phosphoric anhydride in a temperature range of 250325 C. and the products obtained were converted to aryl-phosphonlc dichlorides by reaction with phosphorus pentachloride. This process for the first time made these compounds practically available, but still left considerable to be desired from the point of cost because in the reaction of the aromatic compound with the hexagonal phosphoric anhydride only one or at most two of the phosphorus atoms reacted with the aromatic compound. The remaining phosphorus had to be removed as phosphorus oxychloride. Another disadvantage with certain aromatic compounds, such as naphthalene or alkyl derivatives of benzene was that the Phosphoric anhydride catalyzed condensation reactions which formed -by-products and therefore lowered the yield.

The phosphonothioie dichloridesiwere prepared in the past from alkyl and aryldichlorophosphines by the addition of sulfur, preferably in the presence of catalysts such as aluminum chloride, or by the aid of thiophosphoryl chloride, or sulfur monochloride. These processes also were not practical because of the complicated and expensive methods for preparing the alkyl and aryldichlorophosphines.

In the copending applicatiou of Chao, Lecher and Greenwood, Serial No. 402,392, filed January 5, 1954, now abandoned, there is described the reaction of phsv fide which, however, has not been chlorinated either. It,

phorus pentasulfide with aromatic compounds, free from polar groups capable of reacting with the pentasulfide, the reaction temperatures ranging from 140-250 C. Hydrogen sulfide was evolved and primary reaction products were formed in which the ratio'of phosphorus to aromatic radicals entering the reaction is substantially stoiehiometrical, thus effecting a marked saving in the utilization of phosphorus over the reactions of phosphoric anhydride with aromatic compounds. The primary reaction products were hydrolyzed to give phosphonic acids.

2,870,204 Patented Jan. 20, 195? The present invention utilizes these primary reaction products of the Chao, Lecher and Greenwood application as starting materials and produces phosphonothioicdichlorides and tetrachlorophosphoranes by chlorination of the reaction products of phosphorus pentasulfide with.

aromatic compounds or as will be described belowalso with certain other hydrocarbons containing double bonds. The reaction proceeds readily and either product can be prepared, dependi g on the amount of chlorinating agent used, i r Previously obtained crude reaction products of phosphorus pentasulfide with various hydrocarbons have never been subjected to the action of chlorinating agents. .Pure thionophosphine sulfides have notbeen-known with the single exception of A -cyclohexenylthionophosphine sul- Was unpredictable how compounds of this type (RPS would behave with chlorinating agents and it was surprising that they could be so smoothly subjected to the transformations ,disclosed in this application I. THE PHOSPHONATION REACTION with special case and give very high yields of pure primary reaction products. This is surprising because ether groups are reactive with phosphoric anhydride. It isnot known why there is no significant reaction of the ether group with phosphorus pentasulfide, and the invention is not limited to any theory of whythe phenol ethers react with such ease and without any substantial attack on the ether group.

' Not only aromatic hydrocarbons can be subjected to this reaction but also aliphatic hydrocarbons containing one double bond and monocyclic hydrocarbons containing one double bond, such as commercial isooctene (diisobutylene), butene-l. and -2, isobutene (isobutylene), cyclohexene, cyclopentene, etc. The reaction temperature will vary with the compounds; thus for example, some of the phenol ethers such as anisole react very smoothly and quantitatively at about the boiling point, naphthalene gives best results at about 160-180, but, on the other hand, benzene and some of its homologs such as o-xylenerequire temperatures of about. 225 for best results. Olefins and cycloolefins react at lower temperatures, e. g. diisobutylene at about 100 and cyclohexene slowly. at about In general, With each compound it is desirable to operate at as low a temperature as possible in the range .of optimumtemperatures, i. e.,as low temperatures as produce reason-. ablyfast evolution of hydrogen sulfide, Higher temperatures in the case of each compound, --while still giving good yields, are less desirable as there is some elfect'on the yield and purity of the primary reaction-products obtained. .1 A very important and critical requirement is the; use of a large excess of the compound'tobe phosphonated. In general, the excess should be at least 5 moles per-mole of P 8 but in some cases, like in thatof cyclohexene, a much larger excess is necessary, j The main reaction proceeds according-to the equation reactions take place in varying degrees with some'aromatic compounds resulting in the'productionj of lower s'ulfides of phosphorus'which are not reactive. 'In' the case of ethers of-monocyclic, monohydric phenols, this side reaction is: insignificant, but with benzene and naphthalene it takesplace to a considerable extent. When a sparingly solublew lower sulfideof phosphorus is formedit crystallizes together with the aromatic sulfide contaminating the latter- This'is of little. consequence if it is to be used as inter mediate in the chlorination to give a tetrachlorophosphorane or phosphonothioic dichloride since the thiophos-- phoryl chloride formed as by-product from'the phosphorus sulfides is easilyremov'able.

Some ofthe arylthionophosphine sulfides, in particular,. p-anis'ylthionophosphine sulfide, tenaciously retain the solvent from which they have been crystallized. It can. be removedonly by drying under reduced pressure at. elevated temperatures. We are apparently'dealing with. rather stable clathrate compounds. Thus p -anisylthiono-- phosphiue sulfide 'crysta'llizedfrom anisole and dried in. avacuum desiccator at ordinary temperature still contained' about 12% of anisole;- after recrystallization from. odichlorobenzene and Washing with benzene it contained about 7% benzene which'was even more tenaciously held. than the anisole. This phenomenon is of no consequence in the further use of these products in the process of this.- invention. I

The molecular weight of p-anisylthionophosphine 5111'.- fide, determined on a sample entirely freed from solvent,

indicated a dimeric compound. Likewise the molecularweight'determination of phenyl thionophosphine sulfide indicated a dimer when the occluded solvent was taken. into account.

In the reaction of anisole with P 8 the latter attacks: predominately the nucleus. However, to a very minor extent it attacks also. the methoxy group as evidenced by the formation of some methyl mercaptan when the mother liquors from the crystallized thionophosphine: sulfide are hydrolyzed.

The reactivity of different aromatic compounds varies and so does the yield of the thionophosphine sulfide. It is highest withlower alkylphenol ethers such as anisole- However, in each case the yield is superior to that obtain-- able by the reaction of the aromatic compound with hexagonal phosphoric anhydride. In the case of the phosphonation of olefins and cyclo oleiins the double bond is not directly affected and is still present in the primary reaction product 'and its chlorinated derivatives. The reaction of cyclohexene with phosphorus pentasulfide is known in the art and it has been shown that the phosphorus is not attached to a carbon atom participating in the double bond but ratherto a neighboring carbon atom.

' During the reaction, at least partly in its first stage, the presence of large amounts of oxygen is undesirable. In large scale equipment the free air space-for example, in suitable autoclaves-is so 1 small that no serious precautions need be taken. Howeven in smaller equipment an inert gas atmosphere is preferable.

It is anadvantage that a commercial grade of phosphorus pentasulfide can be used. The use of a very pl re grade offers but little advantage. The lower sulfides of phosphorus such as P 8 or P 5 do not phosphonate aromatic compounds such as anisole. When they are used together with sulfur, P 5 is formed and such mixtures are therefore the chemical equivalents of P 5 However,'there is no 'advantage'in using such mixtures and the yields obtained'with pre-formed' P 51 are generally better. It'is also possible to use elemental phosphorus and sulfur but this does not offer advantages.

The primary reaction products are isolated by filtration if sparingly soluble, otherwise by evaporation of the excess of the compounds subjected to the phosphonation reaction.

11. THE CHLQRINATION REACTION Accordingrtothe present invention, the primary reaction products dealt with in the foregoing chapter are subjected certain" other crude reaction products of'hydrocarbons are mixtures.

- Step 1 Chlprlus t s ll zonto- PO12 agent Step 2 S Chlorinll s i CH30- P 012 CHsO. PO14 agent With the exception of sulfur monochloride, the abovernentioned chlorinating agents can perform 'both'stepsand it depends upon the amount of the agent whether the reaction stops at the stage of'the phospho'no thioic dichloride or'proceeds part or all the way to the tetrachlorophosphorane. At' ordinary or slightly elevated temperature sulfur monochloride'performsonly Step 1.

In these chlorination reactions sulfur is replaced by chlorine. The sulfur is removed as elemental sulfur when sulfur monocfiloride is used or as thiophosphoryl. chloride When phosphorus pentachloride is used.""When chlorine, sulfur dichloride or sulfuryl chloride are used, it depends upon the ratios of the reactants whether the removed sulfur appears as such or assulfur monoor dichloride; in'the case of s'ulfuryl chloride also sulfur dioxide and thionyl chloride are formed. At any rate, the inorganic chlorides formed as by-products hoiluriuch lower than the desired organophosphorus compounds and therefore are easily removable. Any elemental sulfur formed can be separated because of its low solubility in most organic solvents. Because of its low cost chlorine is the preferred agent for practical purposes.

Most reactions proceed at room or slightly elevated temperature but may be completed at the reflux tempera,- ture of the solvent used.

For maximum ease in practical operation, it is desirable to carry out the chlorination in an inert diluent such as highly halogenated hydrocarbons, for instance carbon tetrachloride, phosphorus oxychloride or other inert liquids. v v As 'has been pointed out above, the amount of chlorinating agent will vary, depending on whether it isdes'ired to produce a phosphonothioic dichloride or the corresponding tetrachlorophosphorane; In the" former case essentially stoichiometric amounts 'of' the chlorinatin'g agent are used. In ,the latter case larger amounts are necessary. The primary products from the phosphonation reaction are generally not soluble in carbon tetrachloride, but the phosphonothioic dichlorides, as formed, gofinto solution. It is an easy matter to recover thernf after 7 removing the solvent and inorganic 'by-products by distillation, since the phosphonotioic dichl'or'ides for the most part can' be distilled under reduced pressure. v

I When it is desired toproduce phosphonic di-chlorides, an excess'of the 1chlorinating1agent is used to produce the tetrachlorophosphoranes andv this sometimes results' 'in' a r p c nitati nbf th Ph sp o us cbmitqliiids in he form of thetetrachlorophosphoranes, some of which are not readily so'lublej'in the reaction medium, such as carbon tet a h e- In. uc ase th trachl rcphosphb may be isolatedbefore itsconve'rsi n into 'the'fphosphonic dichloride, but this islhot necessai y and the crude chlorine: tion mixture canjbe'treatedwithsulfur dioxide or droe. ct the use sa h as w s: Ma -ea t. ac 1 es e ne a I enl e sa ient snaz nsr s ei br Produ ts a ci d aft and e desired mean isrecovered by distillation under reduced pressure-gz hiti' a i process is shown for the tetrachlorophosphorane from anisole by the following reactions:

The invention will be illustrated in greater detail in the following specific examples in which the parts are by weight unless otherwise specified.

Example 1 PHENYLPHOSPHONOTHIOIC DICHLORIDE C H PSCl The inorganic acid chlorides are removed by distillation and the phenylphosphonothioic dichloride is distilled under reduced pressure. I

The dichloride is converted by known conventional processes into the ethyl-4-nitrophenyl ester which is a well-known insecticide.

Example 2 PHENYLPHOSPHONOTHIOIC DICHLORIDE C H PSCl The primary reaction product of benzene and phosphorus pentasulfide is prepared as described in Example 1 and slurried in 239 parts of carbon tetrachloride. Then chlorine is introduced until a clear solution results in a slightly exothermic reaction. The carbon tetrachloride and the sulfur chlorides produced in the reaction are distilled off and the phenylphosphonothioic dichloride is recovered by distillation under reduced pressure.

Example 3 PHENYLPHOSPHONIC DICHLORIDE C H POCl Chlorine is passed into a solution of 11.97 parts of phenylphosphonothioic dichloride in 39.9 parts of carbon tetrachloride until no temperature rise is noted. A flocculent white precipitate of phenyltetrachlorophosphorane is formed. Then sulfur dioxide is passed into the solution to form the phenylphosphonic dichloride. The latter is isolated by distilling off the carbon tetrachloride and the inorganic chlorides and distilling it under reduced pressure.

The dichloride is converted by customary processes into the diallyl ester which is known as a starting material for the'preparation of flame-resistant resins. (See J. Am. Chem. Soc., vols. 70, p. 186; 76, p. 2191; and Ind. and Eng. Chem., vol. 40, p. 2276.)

Example 4 2-NAPHTHYLPHOSPHONOTHIOIC DICHLORIDE 8 ll P 012.

V 640 parts of naphthalene and 44.4 parts of phosphorus pen'tasulfide are heated with stirring at a temperature of 6 165170 C. until the evolution of hydrogen sulfide ceases. The reaction mixture is cooled to C. and 440 parts of benzene is added. The precipitate which has formed on cooling is filtered off and thoroughly washed with benzene.

12.15 parts of the crude Z-naphthylthionophosphine sulfide thus obtained is slurried in parts of carbon tetrachloride. Chlorine is introduced until the solid disappears and a clear yellow-orange solution is obtained.

The sulfur chlorides and carbon tetrachloride are removed by distillation after which the Z-naphthylphosphonothioic dichloride distills at 173-174 C. (4 mm.) The product solidifies on cooling, melting point 3841 C. The yield is excellent.

Example 5 p-ANISYLPHOSPHONOTHIOIC DICHLORIDE s ll CHRO OPCIZ temperature (-155 C.) until the evolution of hydrogen sulfide ceases. The reaction mixture is cooled and the precipitate which has formed is filtered off and washed with benzene. The dimeric p-anisylthionophosphine sulfide thus obtained melts at about 225.

12.28 parts of the'crude product is mixed with 84 parts of phosphorus oxychloride. '14 parts of phosphorus pentachloride is added slowly. The product dissolves gradually, forming a clear yellow solution. This solution is then refluxed for one hour. Sulfur dioxide is passed in to destroy excess phosphorus pentachloride. The inorganic chlorides are' removed before the desired panisylphosphonothioic dischloride is distilled as a light yellow liquid at '-157 C. (8 mm.').

This dichloride is converted by conventional means into the ethyl-4-nitrophenyl ester which is an excellent insecticide. In the form of a 1 percent dust, the following percentage kills were obtained: milk weed bug, 100%; confused flower beetle, 95%. 0.1 percent feeding resulted in 100% kill of southern army worm and 90% kill of aphis rumicis.

Example 6 Q p-ANISYLPHOSPHONOTHIOIC DICHLORIDE ornoOP on Example 7 p-ANISYLPHOSPHONOTHIOIC DICHLORIDE CHsOOPCIz 10 parts of the crude dimeric p-anisylthionophosphine 4 sulfide, prepared as described in Example 5, is slurried in' 79.8 parts of carbon tetrachloride. To this 11 parts of sulfuryl chloride is slowly added. A clear yellow solution is formed in a slightly exothermic reaction. After stirring for'one hour at room temperature, the carbon tetrachloride and the inorganic chlorides are distilled off. The phosphonothioic dichloride is recovered by distillation under reduced pressure. I I

i onto-o r on 100 parts of the crude dimeric p-anisylthionophosphine sulfide, prepared as described in Example 5, is stirred with 319 parts of carbon tetrachloride and chlorine is introduced until 'a clear yellow solution results. During the The carbon tetrachloride and the sulfur chlorides are removed and the residue is distilled under reduced pressure.

Example 9 -ANISYLTET ACHLQ'BQ HOSBHORANE AND p-ANISYL- PHOSPHONIC DICHLORIDE oinoO-rou CHsOOPCh 50 parts of the crude dimericp anisylthionophosphine sulfide, prepared as described in Example '5, is slurried in 160 parts of carbon tetrachloride. A steady stream of chlorine is introduced, causing a slight temperature rise. Chlorine addition is continued forfour hours during which the solution turns from a light yellow to a deep red-orange. On cooling and standing, the white p-anisyltetrachlorophosphorane precipitates. Thisis filtered ed and washed with carbon tetrachloride.

This product is put into 8 parts of thionyl chloride and sulfur dioxide is introduced for three hours, c'ausirlgthe precipitate to disappear and leaving a clear solution. After removal of the thionyl chloride by' distillation, the desired p-anisylphosphonic dichlorid'e'distills at 136-138" C. (2-3 mm.).

and

Example 10 p-ANISYLPHOSPHONIC DroHLonIDn CHaO-OP on chlorides have been removed by distillation, the p-anisylphosphonic dichloride distills at 148-"149 C. (5 mm). This dichloride is converted by conventional *rneans into the diallyl ester useful in the preparation of flameresistant resins.

Example 11 A -CYCLOHEXENYLPHOSPHONOTHIOIC DICHLORIDE 5 ll P-Cl:

4.39 parts of dimeric A -c'yclohcxenylthionophosphine transform it into sulfide (J. Am. ChemQS'o'c vol. 74,.p. 4933 (1952) is added to 41.9 parts of phosphorus oxychloride. Gradually 5.2 parts of phosphorus p'entachlo'ride is added with stirring, causing a slight temperature rise. A clear yellow solution results. The inorganic 'chloridesare removed by distillation and then the h -'cyclohex'enylphosphonothioic dichloride distills as a leai,=coIorl$S, l quid at, 94-96 C.(1mm.).

Example 12 ISOOCTENYLPHOSPHONOTHIOIC DICHLORTDES i CsHrsP C12 242 parts *ofcornmercial isooctene (diisobutylene, a

mixture of isomers) and 22.2 parts of phosphorus pentasulfide are slurrie'd together and gradually heated to reflux l5 "temperature. Refluxing is continued until the evolution chlorination the temperature is maintained below 50 C.

removed by distillation and the mixture of isomeric octenylphosphonothioic dichlorides distills from 78-96 C. (2 mm-.).

Example 13 p-ANISY LPHO SPHONOTHIOIC DICH LORIDE S II orno-O-rcn 10.1 parts p-anisylthionophcsphine sulfide, prepared as described in Example 5, is slur'r'ied in parts carbon tetrachloride. To this slurry 33.75 parts sulfur monochloride is added. The solid p-anisylthionophosphine sulfide and sulfiir monochloride react to form a yelloworange solution. The carbon tetrachloride and excess sulfur monochloride are removed by distillation, the latter under reduced pressure.

On cooling, the residue from the distillation partially solidifies. The p-anisylphosphonothioic dichloride is dissolved in carbon tetrachloride, and sulfur formed in the reaction is removed by filtration.

The solvent, carbon tetrachloride, is removed by distillation and the p-anisylphosphonothioic dichloride distills asja light yellow liquid under reduced pressure.

This application is in part a continuation of our copendin-g application Serial No. 423,218, filed April 14, 1954, which is now abandoned.

We claim: I

1. A process which comprises chlorinating the reaction product of P 8 with "a large excess of a compound R-H containing as the desired and major reactive constituents a compound of the formula (RPSQ in which R is the residue of a compound selected from the group consisting of olefins, 'moiiocyclic hydrocarbons having a single double bond, aromatic hydrocarbons and ethers of mono cyclic, monohydric phenols.

2. A process according to claim 1 in which the chlorina- V tionis stopped when approximately two atoms of chlorine have been introduced into the compound (RPS to RPSCI V 3. A process according to claim 2 in which the chlorinating agent is elemental chlorine.

4. Aprocess'ac'cording to claim 3 in which the reaction is eifected in a diluent liquid inert to chlorine.

5. A process according to claim 4 in which the diluent is carbon tetrachloride.

6. A process according to claim 1 in which the chlorination is continued until four atoms of chlorine have been introduced into the compound (RPS M to transform it into RPCl 7. A process according to claim 6 in which the chlo rinating agent is elemental chlorine.

8. A process according to claim 7 in which the reaction is carried out in a liquid which is inert to chlorine.

9. A process according to claim 8 in which the liqu1d is carbon tetrachloride. 10. A process-according toclaim 1 in which the chlo- 5 rinating agent is sulfuryl chloride and the chlorination is stopped when two atoms of chlorine are introduced to transform the compound (RPS into RPSClz.

11. A process according to claim 1 in which the chlorinating agent is sulfuryl chloride and the chlorination is continued until four atoms of chlorine are introduced into the compound (RPS to transform it into RPCl 12. A process according to claim 1 in which the chlorinating agent is sulfur dichloride and the chlorination is stopped when two atoms of chlorine are introduced to transform the compound (RPS into RPSCI 13. A process according to claim 1 in which the chlorinating agent is sulfur dichloride and the chlorination is continued until four atoms of chlorine are introduced into the compound (RPS to transform it into RPCl 14. A process according to claim 1 in which the chlorinating agent is sulfur monochloride.

15. A process according to claim 1 in which the chlorinating agent is phosphorus pentachloride and the chlorination is stopped when approximately two atoms of "iii chlorine are introduced into the compound (RPSQ to transform it into RPSCI 16. A process according to claim 1 in which the chlorinating agent is phosphorus pentachloride and the chlorination is continued until four atoms of chlorine are introduced into the compound (RPS to transform it into RPCl 17. p-Anisylphosphonothioic dichloride.

l8. A -cyclohexenylphosphonothioic dichloride.

19. An isooctenylphosphonothioic dichloride.

References Cited in the file of this patent UNITED STATES PATENTS 2,466,276 Ritter Apr. 5, 1949 2,672,459 Kuh et al Mar. 16, 1954 2,683,168 Jensen et al. July 6, 1954 2,685,603 Walsh Aug. 3, 1954 2,724,726 Craig Nov. 22, 1955 

1. A PROCESS WHICH COMPRISES CHLORINATING THE REACTION PRODUCT OF P4S10 WITH A LARGE EXCESS OF A COMPOUND R-H CONTAINING AS THE DESIRED AND MAJOR REACTIVE CONSTITUENTS A COMPOUND OF THE FORMULA (RPS2)2, IN WHICH R IS THE RESIDUE OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF OLEFINS, MONOCYCLIC HYDROCARBONS HAVING A SINGLE DOUBLE BOND, AROMATIC HYDROCARBONS AND ETHERS OF MONOCYCLIC, MONOHYDRIC PHENOLS. 